which forum do I post this in
If you are messaging back and forth with someone over rMail (which is private-ish), that's a different matter than posting for help in GPIA (a specific public RPoL Forum for GM questions, that has it's own rules, i.e., where you would post it if you were allowed to post it anywhere on a public forum in RPoL). That said, you can report someone through rMail to the Mods if there is an issue that needs their attention for abuse, etc. There's a little link in the top right of messages.